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2011 September 24

iPad Oscilloscope

Filed under: Uncategorized — gasstationwithoutpumps @ 13:52
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Last year, I complained about the lack of oscilloscope attachments for Apple computers, particularly Mac OS X laptops and iPads.  Now there is a product for iPads: Mixed Signal Oscilloscope – iMSO-104 | Oscium.

For $300, you can get a single-channel 5MHz scope (plus 4 digital inputs) that uses the iPad as a display.  It can also be used with the iPhone and iPod touch, though the smaller screens may reduce the value of the scope.

The biggest limitations seem to be

  • single channel
  • only 5MHz bandwidth
  • limited voltage range (up to ±40v with the 10x switch on the probe)
  • only 8-bit resolution (so you need to set the gain carefully)

These limitations are fine for low-power audio work, but not for anything higher speed (like video or even low-speed digital work like an Arduino).  I can’t see this limited device replacing my Kikusui COS5060 bench oscilloscope (60Mhz 2-channel), which I got used for far less money.  It would be nice to have a digital storage scope, but I’m not willing to give up quite so much bandwidth and flexibility to get one.

The core hardware is a system-on-a-chip, the  Cypress PSoC 3 chip, and the software is available as a free app.  I’ve not bothered downloading the software, but reviews on the web suggest that it is a fairly clean, easy-to-use interface, as one would expect from a touch  screen interface to a device with fairly simple, limited capabilities.

ThinkGeek’s catalog says

Intuitive hand gestures are used to navigate:

  • Trigger Level – Setting the analog trigger level is as easy as touching the right side of the screen and swiping either up or down.
  • Zooming – Changing the vertical & horizontal scales can be done by moving two fingers away from each other. To zoom out, simply pinch the screen moving two fingers toward each other.
  • Repositioning Channels – Both the analog and digital channels are also easy to reposition. Touch and swipe the desired channel to any position on the screen to customize your display.

I hope that in the next couple of years we see some more capable (professional, rather than hobbyist) scopes coming out for tablet computers, as the touch screen interface is a natural for oscilloscopes.

2010 November 13

Why no digital oscilloscope for Macbooks and iPads?

Filed under: Uncategorized — gasstationwithoutpumps @ 00:08
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This summer I was playing a little with electronic hardware (something I’ve not done much since I left computer engineering as a field) and was wishing I had an oscilloscope at home.  I don’t want one of the huge old CRT oscilloscopes, like the Heathkit that my brother and I assembled as kids (I don’t remember the model number, but looking in the Heathkit Virtual Museum, I think it was the OM-11).  Neither do I want one of the little pocket oscilloscopes that look like graphing calculators, with the same sort of low-quality screens and fiddly interfaces.

What I’d like is a USB device that handles the analog part of a digital storage scope that plugs into my laptop and uses the laptop for storing, processing, and displaying the signals.  There are dozens of USB oscilloscopes on the market, but so far as I could tell, none of them had software that would run under Mac OS X.  I found this a little surprising, as the Mac OS X machines are much more popular with computer scientists and bioinformaticians than Windows machines are, and I thought that computer engineers would have established a market for USB scopes for Macbooks.  It is true that most of the EE students and faculty I know who would be competent to design the analog electronics for a USB scope do not have the programming ability to design multi-platform software.  I guess that the small companies that sell digital scopes don’t have the resources to hire two engineers (one to design the hardware, another to design the software), and so make do with half-assed designs that only run on one operating system.

I think that there is a market out there for USB scopes that can work with any of the common laptop platforms (Windows, Mac OS X, and Linux).  In fact, an all-software solution that works with several of the existing USB hardware devices would be ideal.  This seems to me like a great project for a computer engineering student who enjoys writing device drivers and working out communications protocols with hardware that was probably designed with no attention at all to the needs of software engineers.

If someone is looking for a hardware project, I think that the iPad looks like a great device to be the screen of an oscilloscope.  This would require a digital storage scope that is not a USB device but uses the weird iPad/iPhone/iPod connector.  It would probably need its own rechargeable battery, as the iPad is not going to provide much power.  I don’t currently own an iPad, and have no plans to get one, but if someone came out with a great oscilloscope based on it, I might get one just for that app.

UPDATE: December 2012

I bought a USB oscilloscope that does work with Mac OS X (the BitScope Pocket Analyzer).  Screenshots and comment at FET threshold tests with Bitscope.

UPDATE: January 2017

I bought a much better USB oscilloscope, the Analog Discovery 2 by Digilent, which works with Mac, Windows, and Linux computers. Both the hardware and the software are much better than the BitScope (which has not improved much in the intervening 4 years). Digilent has an excellent academic discount program also. I have a series of posts using the Analog Discovery 2.

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